Kiln



Dec. 30, 1952 J. FROST ET AL KILN 3 Sheets-Sheet 1 Filed Sept. 15, 1948 Jack Frosf Alex 7." Mick/e Palmer 1?. Pa f/ey JNVENTORS A TTORNEYS Dec. 30, 1952 FR E AL 2,623,740

KILN

Filed Sept. 15, 1948 I 3 Sheets-Sheet 5 Fig. 7

Fig. 8

Jack Frosf Alex T. Mick/e Palmer 5. Parley INVENTORS A TTORIVE Y S Patented Dec. 30, 1952 KILN Jack Frost, Alex T. Mickle, and Palmer R. Pettey,

Dallas, Tex.; said Mickle and said Pettey assignors to said Frost Application September 15, 1948, Serial No. 49,434

4 Claims. 1

This invention relates to improvements in kilns and refers more particularly to tunnel type kilns wherein material to be treated is conveyed through a tunnel type furnace upon a conveyor which also provides the hearth for the kiln. The apparatus of this invention is especially adapted for, but not limited to, use in the manufacture, handling or processing of bulky materials at such elevated temperatures as to preclude the use of exposed metallic surfaces as for example: lightweight or bloated aggregates, or heat treatment of minerals, clays, shale, ores, slate and the like. In treating the above materials, temperatures of 1800 F. to 2700 F. and even higher are usually employed.

In kilns heretofore used for heat treating bulky materials at extreme high temperatures difficulty has been encountered in conveying materials through the heat treating chamber. This is especially true where attempts have been made to employ tunnel type kilns for this use. In the usual tunnel type kiln for treating such materials conveyor chains have been employed for conveying the material to be treated through the furnace. However, due to the elevated character of the temperatures within the furnace it has been necessary to utilize a conveyor made of refractory blocks or the like so that the metal parts of the conveyor are protected from the high temperatures within the furnace. These have not proven satisfactory because the blocks are quickly broken as they are thrown around the rollers upon which the chain is mounted or are broken as a result of thermal shock. Attempts have been made to utilize other conveyances such as cars having a refractory lining and which are advanced through the kiln. This apparatus and method has two main disadvantages besides the initial high cost of equipment namely, the slowness of operation and the fact that the heat requirement is so great as to be impractical because the refractory absorbs so much heat in passing through the kiln which is dissipated to the atmosphere when the car has been discharged from the kiln. This latter distadvantage is also present in the refractory covered chain conveyor.

An object of this invention is to provide a kiln of the tunnel type for use in heat treating bulky material.

Another object is to provide a kiln for heat treating bulky material wherein the refractory conveyor surface remains within the furnace thereby reducing the heat requirement of the furnace and making it possible to eliminate the partial cooling step at and within the furnace theretofore required to protect the refractory hearth from thermal shock.

A further object is to provide a kiln having a hearth with a refractory surface of the tunnel type wherein reciprocal movement of the hearth longitudinally of the furnace is employed for conveying the material to be treated.

A still further object is to provide a kiln of the tunnel type wherein the hearth has a refractory surface and is reciprocated and the movement characteristic of the reciprocation is different in one direction than in the other direction thereby advancing material upon the hearth toward one end thereof.

A still further object of the invention is to provide a tunnel type kiln with a hearth having a refractory surface having a longitudinally reciprocating hearth with means for abruptly arresting movement of the hearth in one direction whereby material carried upon the hearth is advanced therealong toward one end thereof.

Yet another object is to provide a tunnel type kiln having a refractory covered hearth mounted for longitudinal reciprocation within the kiln with shock absorbing means for arresting movement of the kiln in one direction wherein the shock absorbin means may or may not be resilient dependent upon the requirements.

Yet a further object is to provide a tunnel the underside of the material carried through the furnace.

Another object of the invention is to provide a hearth adaptable for use on a tunnel type kiln wherein the hearth has a plurality of surfaces gradually inclined toward the discharge end thereof and extending transversely of the kiln with abrupt faces joining the high and low edges of adjacent surfaces and wherein fluid may be discharged into the interior of the furnace through the abrupt faces if desired for purposes of heating or controlling the character of the atmosphere within the kiln.

Other and further objects of this invention will appear as the description proceeds.

In the accompanying drawings which form a part of the instant specification, are to be read in conjunction therewith, and wherein like reference numerals are employed to designate likea hearth and its mounting for a kiln embodying this invention;

Figure 2 is a sectional view taken along the" line 2-2 in Figure 1 in the direction of the arrows;

Figure 3 is a view taken along the line 33 in Figure 1 in the direction of the arrows;

Figure 4 is a cross sectional view upon a large scale looking in the direction of the inlet for material to be treated inthe kiln shown in Figure 1 and taken along the line d-t in Figure '7 in the direction of the arrows;

Figure 5 is a view illustrating a modified form of hearth the view being the same as if it were taken along the line 5-5 of the hearth of Fi ure 4 were the Figure 4 hearth of the modified type;

Figure 6 is a diagram showing the means for actuating or reciprocating the hearth of the apparatus shown in the foregoing fi ures;

Figure '7 is a view taken along the line 'l-l in Figure 4 in the direction of the arrows; and

Figure 8 is a view taken along the line 8-8 in Figure 7 in the direction of the arrows.

Referring to the drawings, more particularly Figure 7, it will be seen that the kiln, generally speaking, is made up of an elongate tunnel ty e furnace. H3, an elongate hearth I l extending therethroughand having a movable mounting therein upon the support members I2 and actuator means l3 for imparting a reciprocal move ment to the hearth II. It is contemplated that furnace l9 and hearth Il may be constructed in sectional prefabricated parts and assembled togethr 'ata po nt of installation or may be built as integral units.

"Referring to the large views of Figures i and '7 it is seen that furnace H] has an arched roof is constructed of wedge shaped refractory bricks and side walls I5 and It also made up of refractory material. The furnace structure is supported by ground support members ll which may be upright I-beams supported between I-beams l8 and I9. Other suitable steel work may be employed such as uprights 2!], horizontally disposed angle irons 2|, and the like.

'At the inlet end of the kiln there is stationed V a hopper 22 for feeding material into the kiln through chute 23. A guillotine type door 2 lined with refractory material blocks the up er portion of the inlet to the kiln to reduce the loss of heat from the kiln and may be raised by conventional lifting apparatus, not shown in the drawings, with which the door is connected through cable 25 to facilitate access to the interior of the furnace for purposes of repair.

It is often desirable to provide a plurality of openings for charging material to be treated into the furnace. A second opening is shown at chute 26 with hopper 21 associated therewith. A low hanging arch 2%, which may be constructed of wedge shaped bricks, is provided to protect the exposed end of chute 26 from the fire between the chute and burners 29 located in the furnace adjacent the inlet end thereof.

Turning now to the details of the hearth II the hearth has an under supporting metal shell made up of bottom plate 30, side plates or channels 3i and angle irons 32. This metallic shell has formed or built therein a refractory material lining 33 which is preferably steel reinforced by bolts 3% extending through the bottom shell and embedded in the refractory material but not extending through the refractory material. The refractory lining for the hearth may be made up of a plurality of superposed layers of refractory cement or the like and may be cast in place where desired.

A plurality of electrical heating elements,v as for instance resistors 35, may be embedded in the refractory material adjacent the upper surface thereof and connected by conductors 36 and ill to a suitable source of current not shown in the drawings. The heating elements 35 are for the purpose of adding heat to the material treated from the hearth by means carried by the hearth and primarily serve to heat the underside of the material being treated. The main source of heat for firing the furnace of course comes from heating elements carried by the furnace, which may be burners 29 distributed along the furnace at desirable intervals for introducing fuel such as gas, oil or powdered coal into the furnace. The openings l5a and [ta in the walls of the furnace provide access to the heating elements 3,5 to facilitate making of the electrical connections and the like.

In order to reduce the loss of heat from the furnace and to protect supporting members and operating mechanism sand seals are provided between the hearth and the walls of the furnace. The sand seals include metallic channels 38 secured to the furnace walls by angle irons 39 and depending flange or plate members ll! carried by channel members 3|. The flanges it extend into the channels 38 and are buried in sand carried by the channels. The flanges are free to move longitudinally of the channels and are capable of limited vertical movement relative to the channels to accommodate reciprocation of the hearth and still maintain the seal. The metallic parts of the sand seal mechanism are protected from the excessive temperatures of the furnace by the body of refractory material shown at M which extends into recesses in the walls l5 and is of the furnace.

With regard" to the mounting for hearth I! it must be such as toaccommodate reciprocal movement of the hearth in such fashion as to advanc material along the hearth toward one end thereof. This may be accomplished by pivotally securing the hearth to the upper ends of support members i2 providing stationary pivots to the lower ends of these members. The channels 3| are secured to ears 42 which carry shafts or pins 43 to provid the pivotal mounting between the hearth and the hers. At the lower ends of the members; stasup'port merh- V 5 tionary support elements 43 carry yokes 44, through which shafts 45 extend to pivot the members l2 thereto.

With the above arrangement it will b readily appreciated that the hearth may be rocked longitudinally of the furnace. Any suitable arrangement or mechanism for rocking the hearth may be employed so long as the movement is such as to provide different movement characteristics to each direction of movement so that material carried by the hearth will be advanced toward one end of the hearth. A preferred methd and mechanism for rocking the hearth is illustrated and comprises power cylinders 45 having a pivotal mounting on A frames 4! and having pistons therein connected by piston rods 48 to the hearth by means of a pivoted connection between the piston rod and a depending ear 49 secured to transverse channel members 56 supported between cars 42. Inasmuch as the ars 42 are connected to the hearth reciprocation of the pistons within the power cylinders 46 will rock the hearth. Connections 5| alternately supply and exhaust power fluid to the ends of the cylinder to actuate the piston. Either pneumator or hydraulic power means may be employed.

In Figure 6 there is shown a diagram of the system for supplying actuating fluid to cylinders 46. It includes a pump 62, a reservoir 63 for power fluid and a suitable four-way valve 64. The pump, reservoir and valve are connected together by the conduit shown and the valve also has connection to lines 5|. A suitable intermitter or mechanism for changing valve 64, not shown in the drawing but constituting conven tional equipment, operates to successfully connect one of the conduits 5! with the conduit leading from the valve to the pump and the conduit leading from the valve to the reservoir. Where the power fluid is liquid it doesnt matter whether the pump discharges into the reservoir or from the reservoir, but where a pneumatic system is employed the pump will pass the expended power fluid into the reservoir maintaining a sufficient pressure therein to actuate the pistons within cylinders 46.

While it is contemplated-that the different characteristics of the movement of the hearth in opposite directions can be provided by direct energization of the cylinders, it is preferred to power both ends of the cylinders the same and provide means for abruptly interrupting the movement of the hearth in one direction. Preferably this means is of a shock absorbing character and may or may not be resilient depending upon the requirements. The interrupting means or bumper means may include a bumper element 52 secured to a block 5-3 to which the power cylinder is bolted and which has a pivotal mounting upon shaft 54 supported by A frame 47. Bumper elements 55 are carried by the hearth and adapted to engage bumpers 52 when the hearth is rocked in a direction to the right as viewed in Figure l to arrest movement of th hearth in this direction. The bumpers 55 may be secured to the hearth by gussets 5B welded directly to the hearth plate as and include receptacles 5'5 welded or otherwise secured to the gussets and which may constitute a channel section. The shock absorbing elements are retained by receptacle 51 and may be a plurality of arched spring leaves 58 secured within the receptacle by bolts 59. The bumper 52 prefereably has a recess in its bumper face for receiving the head of bolt 55.

When the leaf springs 58 are employed the bumper element will impart a rebound to the hearth when movement in one direction of the hearth is arrested, due to the inherent resiliency of the spring members. This latter movement is desirable where the material being treated does not readily move or slide along the top surface of the hearth. Where the material treated is round or granular and tends to readily move relative to the hearth it is desirable to eliminate the rebound and to merely cushion the shock occasioned by arresting the movement of the hearth. This may be done by providing a plurality of plates 58 which are not bowed, as shown in Figure 7. The air film trapped between the plates serves as a cushion, but does not impart a rebound to the hearth. Oil films also may be employed between these plates when desired and provide the same function as do the air films.

In many instances it is desirable to agitate the material advanced along the hearth in order to more evenly distribute the heat to the material treated. Agitator elements 68, preferably in pairs, are distributed longitudinally of the kiln and extend substantially transversely thereof. These elements preferably are formed of refractory material and may have a mounting upon steel or other metallic members 6| which preferably are non-round tubular members which prevent rotation of the element Ell thereabout. The ends of members 6| are suitably mounted in the walls of the furnace and may be connected to a means for supplying a fluid thereto for cooling purposes. Water or gases may be used for this purpose and it is contemplated that gas such as air or fuel to be used in the furnace may be passed therethrough as a coolant and in this preheated condition then passed into the furnace.

The agitator elements have parts that extend downwardly in close proximity to the upper surface of the hearth and are adapted to be engaged by the material being heated as it passes along the hearth. Preferably these parts include teeth 60a. Where pairs of the agitator elements are employed the teeth 69a of adjacent agitator elements are turned in opposite directions as shown in Figure 8 to provide a tortuous path. These teeth have rounded surfaces 602) which are first contacted by the material being heated and do not hold up the travel of individual pieces of material treated, but direct them into the spaces between adjacent teeth. The arrangement of the teeth shown in Figure 8 gives a double change of direction to the path of travel of the material similar to the action of a gang plow in ground working tools and engagement of each of the teeth by material being heated moves the material somewhat transversely of the hearth. The plurality of agitator elements or pairs thereof distributed along the hearth insure proper and complete exposure of the various particles passing through the kiln to the head of the furnace.

Referring to Figure 5 a modified refractory lining for the hearth is shown. The hearth, except for the changes shown in the figure, may be the same as in the other figures of the drawings. The modification primarily is concerned with the surface of the hearth which is exposed to the interior of the furnace. In this modification the surface is actually a plurality of surfaces 65 gradually inclined toward the discharge end of the hearth. The high and low ends of adjacent surfaces 65 are joined together by abrupt, substantially vertical faces 66. A plurality of conduits 5! may open along faces 66 and are dis- 4' tributed transversely of the faces. These conduits' 6 are connected to a manifold 63 in turn having a flexible connection with a source of fluid under pressure. This source of fluid is not shown in the drawings, but may comprise combustible material such as natural gas, fuel oil or even powdered coal and provides a means carried by the hearth for heating the material carried along the hearth. Also this construction is useful where it is desired to control the character of the atmosphere within the furnace, that is to make it either oxidizing or reducing in character. Where this is true, oxygen, or a reducing gas such as CO, or inert gas such as CO2 may be employed.

In operation thekiln fired up by igniting fuel suppli d by burners 29 distributed along the furnace. The auxiliary heating means carried by the hearth, whether they be the electrical elements 35 in Figure 4 or the burners 577 shown in Figure may also be employed in the heating up operation. Material to be heated, which for the purpose of describing the invention will be considered as shale or clay of a bloatable character for the making of lightweight aggregates, is distributed by hopper 22, and if desired, hopper 2?, upon the hearth. This material is of a granular character or may be in the form of pellets or pugs having diameters approximately up to 1 or even greater. It to be understood that the description with regard to the manufacture of lightweight aggregates is by way of illustration only and not by way of limitation.

The actuating mechanism for rocking or reciprocating the hearth is energized and as the hearth moves towards the discharge end of the kiln the bumpers 52 and 55 engage to abruptly arrest further movement of the hearth in this direction. Preferably the shock absorbing bumpers are employed so as not to place undue shock upon the frangible refractory material. The abrupt stoppage of movement of the hearth causes the material being bloated to slide, roll, tumble, or otherwise move along the hearth toward the discharge end. The hearth then commences the opposite stroke of its reciprocation and with the pivoted mounting and rocking movement the initial return movement includes a vertical component, but this vertical component is very small and both the vertical and horizontal component of movements are readily accommodated by the sand seal comprising elements 33 and Gil shown in Figure 4. This stroke of the rocking or reciprocal movement of the hearth is not abruptly ended and there is little tendency for the material carried by the hearth to move back toward the inlet end of the kiln.

Where the material being treated is difficult to move along the hearth the bumper 55, as shown in Figure 2, is employed. Due to the resiliency of springs '58 this bumper, in addition to abruptly arresting movement of the hearth in one direction, aids in initiating the opposite stroke with the resultant rebound and the material, due to its inertia, tends to remain stationary while the hearth will move thereunder and relative thereto.

The material traveling along the hearth may be heated from above and from below. The heat from above comes from the contact with the products of combustion of the fuel Within the furnace, as from convection and also from radiation from the furnace walls and arched roof. From below the heat is due to radiation and conduction from the refractory material of the hearth which is heated both from the combustion (iii within the furnace, radiation and convection due to this combustion and from the auxiliary heating elements 35 or the burners 5'! as the cases may be.

The distribution of heat to the material traveling along the hearth is substantially uniform and evenly distributed to all particles and all sides of each particle due to the agitation of the particles as they pass beneath agitators 6B. These agitators shift the position of the particles transversely of the hearth and where employed in pairs impart a double shifting to the material at substantially the same station within the kiln.

As the material advances along the hearth its temperature increases and in the case of bloatable material, the materials become plastic as they advance along the hearth and the gases trapped and generated within the particles cause them to bloat into cellular or honeycomb masses. These masses are then discharged from the kiln and in the interest of simplicity the discharge apparatus has been eliminated from the disclosure but may be of any conventional type.

It is contemplated that actuating mechanism other than that shown and described herein may be employed for imparting the desired movement characteristics to the hearth, but the fluid actuated mechanism preferred because it lends itself to ready adjustment to vary the movement characteristics of the hearth to accommodate difierent materials and also because of its low initial cost.

As many possible modifications of the apparatus may be made embodying the invention the matter herein set forth should be interpreted as illustrative only and not by way of limitation, the scope of the invention being defined solely by the claims appended hereto.

Many subc-ombinations of the invention have utility when employed independently of the entire combination and it is contemplated that they may be employed independently in the manner set forth in the appended claims.

Having described the invention What is claimed 1. In a high temperature kiln having an elongate -furnace with a hearth extending therethrough and movably mounted relative to the furnace, said hearth having its surface exposed to the interior of the furnace made of refractory material, means for imparting a reciprocal longitudinal movement to the hearth with difierent movement characteristics in each direction whereby material carried by the hearth will have imparted thereto an overall movement toward one end of the hearth, agitator elements supported within the furnace above and transversely of the hearth and having parts engage'able b'y material being treated as it advances along the hearth, said parts adapted to shift the position of material engaged thereby transversely of the hearth.

2. An arrangement as in claim 1 wherein the agitator parts engageable by the material b'eing treated constitute vertical members carried by the agitator and lriavin faces engageable by the material which are inclined relative to the longitudinal axis of the hearth and spaced just above the upper surf ace of the hearth.

3. An arrangement as in claim 1 wherein the agitator elements are formed of refractory material and mounted on hollow members having fittings for circulatin a cooling -luid therethrough.

4. In a high temperature kiln the structural combination comprising an elongate tunnel type furnace with means for firing same, a hearth extending therethrough and having its surface exposed to the interior of the furnace made of refractory material, said hearth having a pivotal mounting upon the upper ends of support members which in turn have a pivotal stationary mounting, means for rocking the hearth within limits in a vertical plane including the longitudinal axis of the hearth with a movement characteristic which will advance material to be treated toward one end of the hearth, agitator elements supported within the furnace above and transversely of the hearth and having parts engageable by material being treated as it advances along the hearth, said parts adapted to shift the position of material engaged thereby transversely of the hearth.

JACK FROST.

ALEX T. MICKLE.

PALMER R. PE'ITEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS 

